The invention relates to the continuous handling of bulk materials using conveyors fitted with endless flexible belt conveyors. More particularly the invention concerns endless flexible belt conveyors that operate using deep semicircular troughs, said belt conveyors being leaktight to external elements such as rain, wind and pollution to ensure the protection of the transported materials and being capable of enclosing said transported materials, such as salt, powdery products, cement or cereals, to ensure the protection of the sites over which the materials are transported.
At present tubular flexible belt conveyor devices, usually called pipe conveyors or hose conveyors, or mobile sheaths capable of containing and conveying materials are known from among the handling assemblies available intended to provide double leaktightness towards the inside of the endless flexible belt conveyor, on the one hand, and towards the outside, on the other. These type of devices are described in documents WO9511848-A (DUNLOP ENERKA BV and FOERDERANLANGEN MASCHINENBAU GmbH), FR2615836-A (MAREAU), DE2263710(FRENKING and ROSSIG) and U.S. Pat. No. 4,915,213 (AB SCANIANINVENTOR).
These devices present several major drawbacks. Besides the reduction in the sectional capacity of the belt conveyors, and therefore the output they induce, there are difficulties in terms of the means of ensuring effective leaktightness. These difficulties result in runoff water entering the flexible belt conveyors and damaging the transported products with the consequences that this implies when the products are materials that can be affected by water or even humidity, such as cement, cereals, sugar or salt. One of the main problems is a mechanical one relating to the means intended to maintain the endless flexible belt conveyor in a tubular shape, for example in document FR2604983 -A (JAPAN PIPE CONVEYOR), and the means for closing the endless flexible belt conveyor in on itself or closing the flexible cover on the endless flexible belt conveyor near the loading zone and the means for opening said endless flexible belt conveyor near the unloading zone, as disclosed in document EP04223101 (KABUSHIKIKAISHA ISEKIKAIHATSU).
In order to overcome these drawbacks document FR2715538-A (SURRATEAU) proposes sliding said endless flexible bell conveyor on the inner wall of a belt support, that is also tubular, which does not facilitate loading and unloading operations. Another solution is proposed in document FR2615836-A (MAREAU) in which an installation is described that requires not only a guide cable and the endless flexible belt conveyor to be shaped but also grooves and projecting parts that mesh together to close the endless flexible belt conveyor above the cable.
Similarly, document FR270172-A (POIVRE) proposes teeth on the longitudinal edges of the endless flexible belt conveyor to enable them to mesh together, even though the installation described does not require a cable but rollers to shape the endless flexible belt conveyor into a tube.
In order to overcome these drawbacks, particularly to reduce the high maintenance costs resulting from the need to use more or less complex mechanical devices for shaping the pipes or opening and closing the endless flexible belt conveyor, document DE4138780-A (PHOENIX AG) proposes a flexible belt conveyor that uses roller-free device consisting of one or more guide parts, such as belts, plates or rails constituted by anti-friction, polytetrafluorethylene or polyethylene material. Even though the principle is relatively simple this device does not prevent a reduction in the sectional capacity of the flexible belt, and therefore a reduction of the output of the installation, because its pipe-shaped operation does not allow for use of an endless flexible belt conveyor with a deep semicircular trough shape.
Another attempted solution is described in document JP10120136-A (BANDO CHEMICAL INDUSTRY Ltd.) that proposes a covered belt intended to avoid the use of complex mechanical devices to assemble and separate the belt conveyor from its cover belt. In order for this to be achieved it requires a special shape, called a distorted shape, of the cover belt the edges of which are covered with an intermediary belt that is harder than the belt itself. The device also needs air to circulate between the belt conveyor and the cover belt which also requires careful installation of fragile components. In document FR20373472-A the RAYNERI company proposes a device that is also connected to a source of compressed air in order to avoid the materials that are transported in a tube shape from adhering to the surfaces of the belt.
In document U.S. Pat. No. 3,618,746 (GOODYEAR TIRE AND RUBBER COMPANY) a device is described that is doubtless leaktight but that is incapable of operating in the shape of a deep semicircular trough. The same is true for the double-belt devices described in documents DE1140506 (CONTINENTAL GUMMI-WEAKE AG) and U.S. Pat. No. 4,951,806 (SWING).
Besides these drawbacks the above systems are also completely ineffective when the conveyor reaches the maximum degree of slope for the transported material. For this reason, document FR2469365-A (HASHIMOTO) proposes the use of an endless flexible belt conveyor the inner section of which comprises separator parts to prevent the products from sliding when the slope increases. Even though this arrangement may prove useful it has the drawback of requiring the use of special cleated belts that reduce the flexibility, increase the mass and consequently reduce the output of the handling machine.
To date there does not exist therefore a device that meets the double leaktightness criteria, the mechanical requirements of using simple means to facilitate guiding, opening and closing and those of the maximum sectional capacity of the endless flexible belt conveyor operating in the shape of deep semicircular troughs to ensure maximum output.
The technical problem therefore consists in producing a simple, inexpensive continuous handling device comprising an endless flexible belt conveyor that ensures double leaklightness, i.e. that protects the transported material from damage from outside influences, on the one hand, and the environment from pollution caused by the transported materials themselves, on the other. The device should not reduce the sectional capacity, and therefore the output, and should remain usable even when the conveyor reaches its maximum degree of slope for the transported material, i.e. when the endless flexible belt conveyor is required to operate in the shape of a deep semicircular trough without requiring complex, fragile mechanical devices to be installed in order to maintain the shape, opening and closing of said endless flexible belt conveyor.
In order to achieve this the invention consists of an endless flexible belt conveyor that operates in the shape of a deep semicircular trough, provided with a cover belt, which is also flexible, consisting of a light textile support at least one side of which is coated with an elastomer or plastic polymer that, during operation, is held in contact with the carrying side of said endless flexible belt conveyor by pressure rollers, the two said belts moving at the same speed and enclosing the transported material.
The invention is characterized in that, except for the longitudinal edges, said flexible cover belt is flat in the rest position and that its width is related to that of the endless flexible belt conveyor when said conveyor has the shape of a deep semicircular trough, at the angle relative to the horizontal created by said flexible cover belt during operation, and to the length of the continuous leaktight loop that is integrated into each of the longitudinal edges of said flexible cover belt; and in that a leaktight device between said belts is constituted on each of the longitudinal edges of said continuous leaktight loop, the width of the recess of which matches the thickness of the endless flexible bell conveyor that grips each longitudinal edge of said endless flexible belt conveyor by automatically locking near the loading zone; and in that said leaktight device is disconnected near the unloading zone by becoming simply unhooked under the load exerted by the separation between said belts and the trough angle opening without any mechanical operation being required to create said disconnection.
In a preferred embodiment the leaktight device between the flexible cover belt and the endless flexible belt conveyor is characterized in that each continuous leaktight loop is constituted by each longitudinal edge of said flexible cover belt that folds back on itself to enclose the longitudinal edges of said endless flexible belt conveyor.
In another embodiment the leaktight device between the flexible cover belt and the endless flexible belt conveyor is characterized in that each continuous leaktight loop consists of a continuous ridge that is added to each longitudinal edge of said flexible cover belt either by cold or hot bonding or mechanical assembly, said ridge gripping the longitudinal edges of said endless flexible belt conveyor.
In this embodiment each ridge constituting the section of the leaktight device borne by the flexible cover belt either consists of the same polymer material as that which constitutes the coating of said flexible cover belt or of a different polymer material, said polymer material either being an elastomer or plastic.